Field Demonstration of Permeable Reactive Barriers to Control Radionuclide
and Trace-Element Contamination in Ground Water from Abandoned Mine Lands

ABSTRACT

Pump-and-treat methods are costly and often ineffective in meeting long-term
protection standards for contaminated ground water. Permeable reactive barriers
(PRBs) may offer a cost-effective alternative to other ground-water remediation
methods. A PRB functions as a passive in-situ treatment zone that degrades or
immobilizes contaminants. A demonstration project is currently (1999) underway
at an abandoned uranium upgrader operation site in southeastern Utah to evaluate
the removal of uranium from ground water by using six different PRBs. Two methods
of PRB deployment, the funnel and gate design and non-pumping well design, were
installed to passively treat uranium-contaminated ground water. The six different
PRBs have removed uranium from the ground water with various levels of efficiency.
With respect to the PRBs installed using the funnel and gate design, the barrier
containing zero-valent iron has consistently removed more than 99.9 percent
of the input uranium concentration during the first year of operation. The percentage
of uranium removed in the bone char phosphate and amorphous ferric oxyhyroxide
PRBs was slightly less, averaging 94.0 and 88.1 percent, respectively. The three
barrier deployment tubes in the non-pumping wells containing mixtures of bone-char
phosphate and iron-oxide pellets removed less uranium than the PRBs deployed
using the funnel and gate design. Numerous geochemical and hydrological factors
that affect uranium removal efficiencies and processes in each of the PRBs are
currently (1999) being evaluated.